I have finally discovered a video from someone who has the exact same noise I have on cold. Now this noise seems to disappear wen reving up the engine but I have no idea what it could be coming from.

 

That's your dual mass flywheel rattling.

Is it really?

I thought this would be something else..... The thing is, it sounds like it's coming from the left side of the engine as you look at it. 

 

When it gets warm, the sound changes and sounds more like this and it sounds like it comes more from the right/middle side of the engine bay (again as you stand in front and look at it)

 

Yes that metallic rattle sound is classic DMF rattling/failure.

Have a listen to this to compare.

 

Okay - sounds similar but why would it have more frequent and muffled knocks when cold? You can tell the sound is quite different between cold and hot.

 

This is actually a relief for me if it turns out to be true as I initially thought it may be totally unrelated. Having 2 weird noises from different sources under the hood would be a nightmare...

Firstly, don't just accept that it's the DMF - that's a common mistake that a lot of garages make when diagnosing rattles/noises -  the DMF is a symptom and not a cause. If, for example, you have a partially blocked injector, low flow rate on one injector or weak glow plug on one cylinder, you get an imbalance in the crank, leading to DMF noise - changing it will only mask the problem, and it will come back, as the underlying cause hasn't been sorted. The noise will go as you build the engine revs, as you are increasing the rotational speed, so centrifugal force increases, tightening everything up. Same with a fouled injector, as you increase the revs, the fuel delivery pressure increases, evening out the combustion process.

 

You say it comes from the LH side as you look at the engine, to me that says front end drive components. First thing to do then is to remove the aux belt, and ses if that makes a difference, if it disappears then you need to be looking at the rotating components there - my money would be on a seized or failing alternator pulley, a lot cheaper than a DMF.

 

After that, get a decent garage to do some component testing, such as injector flow rates (especially if over 100k miles) to determine a healthy fuel system. It's worth spending a few quid on having the fault diagnosed properly, than having an expensive clutch and DMF replacement, something that may not even be needed.

That makes perfect sense! The car has 234.000 km on the clock.

 

These sounds are accompanied by often occurring judders in the engine at idle, regardless of being cold or warm and totally unrelated to the piston firings. The engine actually has the nice linear crunchy sound of a healthy diesel. It rarely is that I don't feel the judder at idle. However, the car drives remarkably well and pulls like train.

 

 

I am afraid of taking it to a "decent garage" as that would cost almost 100 pounds per hour here in Denmark.... and believe me... they do like to take their time when they work.... It often is a lot cheaper to just change parts here instead of diagnosing and trying to pinpoint the problem... :( In other words... never mind taking the injectors to a tester.... that would take so much time that it may be cheaper to just replace them altogether if they are faulty...

 

I guess I can start with the glow plugs, then the alternator belt...

 

Could this lead to worse problems over time?

Edited 11 November, 20169 yr by Inex

If the source of the vibration/imbalance isn't found and cured, then eventually the DMF will fail and need replacing. With the distance yours has covered, it is probably getting close to the end of it's life anyway. The injection pressure only needs to be down by 10% or so on a common rail diesel to have an effect, trouble is, you won't notice it at idle, or during normal running, as it's not a huge amount - until you realise that 10% of common rail pressure can be as much as 3000psi (roughly 200bar).

The 2.0 diesels with the Seimens injectors (I think) have been known to have injector problems, and quite often need them replacing.

Mine is a BKD PD engine. I have no idea what kind of injectors I have (and I only own the car for 2 months now)

 

Question:

If one of the glow plugs would cause the unbalance, wouldn't this only happen the first 1-2 minutes after a cold start? Until the temperature evens out in the cylinders.

 

I must say that one morning (and this only occurred once) 5 seconds after the engine started, I felt a pretty violent judder for 5 to 10 seconds before returning to the usual judder. Wouldn't this sound more like a bad glow plug? (starting temperature was ~7 C)

Yes, a duff glow plug would cause a lumpy idle while cold, which would disappear when it had warmed up. We have had instances of PD injectors causing lumpy running after high mileage, more so where the incorrect grade of low sulphur oil has been used. I would start with the aux drive first, then work your way along from there.

Thank you so much for taking the time! Will return with answers or questions as I go along.

Surprize, surprize. Guess what I accidentally discovered this morning.

 

The engine is not shaking anymore at idle and the knocks are not as loud if the ECON button on the climate control is turned OFF (not lit up). As far as I know, when you press the ECON button, it won't use the AC compressor, is that correct?

 

If so, why would it stop shaking and knocking when the compressor is ON and not when its OFF?

https://www.dropbox.com/s/f4bub3fm2dp05b5/Screenshot_20161117-093525.png?dl=0

 

This thing is rattling when AC is not on. The one behind the alternator. What is it?

Is it one of these?

 

http://images.lteplatform.com/images/products/600x600/328440890.jpg

 

http://www.eurocarparts.com/ecp/c/Skoda_Octavia_2.0_2005/p/car-parts/belts-chains-and-tensioners/engine-parts/tensioners-idlers-and-dampers/?328440890&1&763a7211513e2e9b51b6390152cad7eeeea263a2&000112

 

It keeps tension in the aux drive belt. The bearings do go on these and they usually shriek/scream/whine/whir. I suppose if the bearings are really shot they'd rattle and bang? Does the belt run smoothly when the engine is idling?

If it sounds like the above videos then it sure does sound like DMF.

 

If so, why would it stop shaking and knocking when the compressor is ON and not when its OFF?

 

When the engine is under more load then it is very plausible it's smoothing it out as reving a few RPMs higher and injecting more fuel.

Is it one of these?

 

http://images.lteplatform.com/images/products/600x600/328440890.jpg

 

http://www.eurocarparts.com/ecp/c/Skoda_Octavia_2.0_2005/p/car-parts/belts-chains-and-tensioners/engine-parts/tensioners-idlers-and-dampers/?328440890&1&763a7211513e2e9b51b6390152cad7eeeea263a2&000112

 

It keeps tension in the aux drive belt. The bearings do go on these and they usually shriek/scream/whine/whir. I suppose if the bearings are really shot they'd rattle and bang? Does the belt run smoothly when the engine is idling?

 

The belt seems to run smooth. I will try to make a video tomorrow morning.

 

 

If it sounds like the above videos then it sure does sound like DMF.

 

 

When the engine is under more load then it is very plausible it's smoothing it out as reving a few RPMs higher and injecting more fuel.

 

Does it get that much more fuel to run the AC compressor? I will try to make a video of my own.

I went to my mechanic for a first impression.

 

He recommends changing all the bearings across the alternator belt (except the crank one). There is apparently a sound coming from the AC compressor bearing and another coming from the tensioner as soon as the AC is turned on. 

To prove all this to me, he sprayed some lubricant on the compressor wheel/bearing and the noise went completely away and the engine stopped juddering. 

 

So far, I am happy it's not a faulty injector or a DMF.

 

At the moment I need to get the parts so... can anyone point me out to the part number for the compressor bearing alone (not the whole compressor)?

I've got my vcds cable the other day and monitored the Idle stabilization for a while with the engine cold and with it warm.

 

I am not exactly sure what I can tell out of it as I can see many people posting about bad injectors etc...

 

 

The results are as follows:

 

COLD:

Cyl1     ~0.60

Cyl2     ~0.14

Cyl3     ~0.05

Cyl4     ~0.84

 

WARM:

Cyl1     ~0.40

Cyl2     ~0.12

Cyl3     ~0.05

Cyl4     ~0.70

 

I still have the judder at idle and the sound is still there (when cold only).

I noticed some puffs of gray smoke when idling too.

 

Could I use the vcds to further investigate this? I would rather not jump into changing flywheels and injectors before I know something.